1. Field of the Invention
The present invention relates to a power converting device and particularly to a power converting device which uses a voltage start unit and a pulse width modulation circuit for performing operations.
2. Description of Related Art
In the design of a server system, application specific integrated circuits (ASICs) are commonly-used integrated chips. Integrated chips perform operations by using an input voltage and a core voltage in the server, and the server converts the input voltage into the core voltage through a power converting device. It is noted that, in order to conform to the logical design of the server, generally the sequence of providing the input voltage and the core voltage is specifically restricted, and the timing of providing the input voltage needs to be earlier than the core voltage.
In view of the above, FIG. 1 illustrates a partial circuit diagram of a conventional server. As shown in FIG. 1, a power converting device 110 switches a conductive state of a switch SW11 and a switch SW12 through a pulse width modulation circuit 111. As the switch SW11 and the switch SW12 are switched, a current flowing through an inductance L11 and a capacitor C11 is changed, so as to convert an input voltage VIN1 to a core voltage VCORE1. On the other hand, the input voltage VIN1 and the core voltage VCORE1 are supplied to and used by an application specific integrated circuit 120 of a conventional server 100. Herein, an inner transistor of the application specific integrated circuit 120 forms a circuit structure equivalent to diodes D11 and D12, and the circuit structure is electrically connected between two terminals of the power converting device 110.
However, the input voltage VIN1 received by an input terminal TM11 of the power converting device 110 may leak to an output terminal TM12 of the power converting device 110 through the diodes D11 and D12. Consequently, when the power converting device 110 is in a soft start mode, the input voltage VIN1 is discharged through the inductance L11 and the switch SW12, as the switches SW11 and SW12 are switched. In the meantime, the levels of the input voltage VIN1 and the core voltage VCORE1 are pulled down simultaneously, which results in the malfunction of the power converting device 110.